Steel Culvert Rehab

DHC has recently completed multiple designs of arch and elliptical shaped steel casings for culvert rehab projects for InfraSteel. Structural load and stress calculations on the new casing sections were performed and submitted, to prove that the steel segments can safely support the full intended loading of the existing deteriorated culverts. Once certified and approved by the governing agency, the casings are installed via the slip lining process as explained on the InfraSteel site:

SLIP LINING PROCESS
The slip lining process rehabilitates a failing culvert without the need to remove the existing deteriorated pipe. During installation, bypass pumping helps to insure an environmental friendly worksite. The slip lining process is completed by installing INFRASTEEL® 242, smooth wall steel pipe, into the existing host pipe, and then grouting the annular space between the two pipes.

Ernest Olin, the resident engineer for NYSDOT Region 7, and Andrew Willard, the senior civil engineer for St. Lawrence County Department of Highways, worked in tandem to complete two large diameter culvert preservation projects. Both entities had large, failing arched culverts that needed repair. Willard had heard about InfraSteel from Precision Pipe and Products, and had mentioned InfraSteel to Olin. They knew thatInfraSteel could match the plate arch shape of the existing structures, providing a smooth wall ID that would not decrease the hydraulic capacity.

Also, because InfraSteel has added copper to the steel for corrosion resistance, and it has out-performed other products in abrasion resistance testing, Olin and Willard were assured a life expectancy of 50 to 100 years.
The state’s project was under Route 12 in the town of Hammond, N.Y. The existing structure was a corrugated plate arch that was installed in the 1960s; it had a 131-in. span and an 81-in. rise with a deteriorated invert that was completely rusted through.

The state’s failing culvert was under 2 ft of cover. NYSDOT structural engineers had ruled out the option of paving the invert because of concerns regarding the structural integrity of that type of repair. InfraSteel’s strength and thickness, coupled with the grouting of the annular space, offered improved structural integrity.

Basing their decision on existing round pipe options, NYSDOT hydraulic engineers deemed sliplining the structure not an option because round pipe would decrease the hydraulic capacity of the existing structure, which was not acceptable.

Since the Manning’s coefficient of InfraSteel’s smooth wall carbon steel is .012 in., which is better than corrugated metal, and because InfraSteel matches the exact shape of the host pipe, maximizing the area of flow, there was no loss of hydraulic capacity. Round liners do not typically provide enough hydraulic capacity to maintain existing capacity in large arched and elliptical structures.

The only other option that the state had for a solution was for the project to become a Job Order Contract Candidate. This would require cutting the road and replacing the existing structure. This method would have taken significantly longer to complete and had an estimated cost of $360,000.

Subsequently, Olin and Willard made a plan to create a shared service agreement that would preserve both of the existing structures and save taxpayers money. They agreed to share both manpower and equipment in order to get the job done. Also by working in tandem, the two failing structures were going to be repaired quickly and economically without the interruption of emergency vehicles and other traffic.

Detailed measurements of the host structures were taken in order to ensure that the shape of the InfraSteel liners matched the host structures. In order for the InfraSteel liner to be manufactured with matching radii of the host structure, the field measurements of the host pipe provided to the manufacturing plant are of critical importance. Precision Pipe has developed a detailed method of measuring and gathering information about the host pipe, which is provided to the manufacturing plant engineers so that they can convert that information into a matching liner. The liner is sized with exact rise and span measurements that allow it to be sliplined into place. Fish baffles and weirs are an option but were not required for these two sites. The plant engineers provided drawings back to the project engineers who signed off on them so that production could begin. The orders were placed with Precision Pipe and Products and the liner sections for the Hammond site were delivered within a few weeks.

InfraSteel is generally manufactured in 8- to 10-ft lengths to facilitate handling and shipping; however, longer lengths are available. Also, the standard .500-in. wall thickness was chosen for these sites, although InfraSteel can be manufactured various wall thicknesses up 1-in. thick.

The combined state and county crew began work preparing the host structure for slip-lining by laying down a simple rail system to facilitate the sliplining process. Two welders from the county worked with two NYSDOT bridge crew welders to weld the InfraSteel joints together. The liner is shipped with cross bracing, which is left in place until the installation and grouting are complete. The bottom section of the InfraSteel liner has an inverted bevel, allowing welding to be done from within the pipe so that welders do not have to get under the liner. The top and sides are welded on the outside. Ventilation was provided to the working space within the pipe. The welding time per joint was approximately two hours.

A 200 series track hoe excavator did the heavy lifting and pushed the liner inside of the host pipe. Even with short working hours during the construction period, the welding and sliplining were completed within a few days.

Grouting was done from within the structure through grout ports. The 2-in. grout ports were cut into the liner at top center, and wherever else deemed needed, which allowed grout to be pumped into the annular space from within the structure. It was also determined that the shoulder of the road could be extended by utilizing additional InfraSteel liner. When the dressing up of the site was complete, the entire installation took only two weeks. The total cost of the sliplining installation was $85,000, providing a savings of $275,000.

St. Lawrence County’s project was under CR 47 and was built similarly; however, there was 15 ft of cover. The existing CMP structure, which was installed in the 1960s, was skewed under the road. Also, there were utilities that would have to have been relocated if the road had been cut. Most importantly, open cutting the road would have required six weeks of road closure, detouring traffic 24 miles to Route 3, costing valuable time to emergency vehicles and the motoring public. An arched pipe liner totaling 104 ft of 97-in. x 61-in. was chosen by the Highway Department to be sliplined into the existing 103-in. x 71-in. culvert. The estimated cost to remove and replace the existing structure was $217,000.

Because St. Lawrence County’s welders had worked with the NYSDOT crew, a good working relationship had been established. Although it is generally recommend to stop the flow of water, by bypass pumping or other means, the St. Lawrence County crew operated with significant water flow, drying up the weld areas of the joints that were welded inside of the existing culvert. The crew welded the pipe together and sliplined it into place in 10 working days. The grouting and clean up took only two days. The actual material and construction cost using InfraSteel was $75,000. Subsequently, there was a direct savings of labor and material of $142,000 and there was the additional cost-savings of the detour to the traveling public of $399,800.

The construction methods used for these two projects saved the taxpayers of New York State and St. Lawrence County more than $816,800, demonstrating how to maximize maintenance dollars through teamwork and cooperation.